NASA's venerable Voyager 1 probe has encountered a strange new region at the outer reaches of the solar system, suggesting the spacecraft is poised to pop free into interstellar space, scientists say.

Voyager 1, which has been zooming through space for more than 35 years, observed a dramatic drop in solar particles and a simultaneous big jump in high-energy galactic cosmic rays last August, the scientists announced in three new studies published June 27 in the journal Science.

The probe did not measure a shift in the direction of the ambient magnetic field, indicating that Voyager 1 is still within the sun's sphere of influence, researchers said. But mission scientists think the spacecraft will likely leave Earth's solar system relatively soon.

Voyager 1 and its twin, Voyager 2, launched a few weeks apart in 1977 to study Saturn, Jupiter, Uranus and Neptune. The probes completed this unprecedented "grand tour" and then kept right on flying toward interstellar space.

Voyager 1 should get there first. At 11.5 billion miles from Earth, the spacecraft is the farthest man-made object in space. Voyager 2, for its part, is now 9.4 billion miles from home.

Both probes are currently plying the outer layers of the heliosphere, the enormous bubble of charged particles and magnetic fields surrounding the sun. But things are really getting interesting for Voyager 1, the new studies report.

On Aug. 25, 2012, the probe recorded a 1,000-fold drop in the number of charged solar particles while also measuring a 9 percent increase in fast-moving particles of galactic origin called cosmic rays.

NASA's venerable Voyager 1 probe has encountered a strange new region at the outer reaches of the solar system, suggesting the spacecraft is poised to pop free into interstellar space, scientists say.

Voyager 1, which has been zooming through space for more than 35 years, observed a dramatic drop in solar particles and a simultaneous big jump in high-energy galactic cosmic rays last August, the scientists announced in three new studies published June 27 in the journal Science.

The probe did not measure a shift in the direction of the ambient magnetic field, indicating that Voyager 1 is still within the sun's sphere of influence, researchers said. But mission scientists think the spacecraft will likely leave Earth's solar system relatively soon.

Voyager 1 and its twin, Voyager 2, launched a few weeks apart in 1977 to study Saturn, Jupiter, Uranus and Neptune. The probes completed this unprecedented "grand tour" and then kept right on flying toward interstellar space.

Voyager 1 should get there first. At 11.5 billion miles from Earth, the spacecraft is the farthest man-made object in space. Voyager 2, for its part, is now 9.4 billion miles from home.

Both probes are currently plying the outer layers of the heliosphere, the enormous bubble of charged particles and magnetic fields surrounding the sun. But things are really getting interesting for Voyager 1, the new studies report.

On Aug. 25, 2012, the probe recorded a 1,000-fold drop in the number of charged solar particles while also measuring a 9 percent increase in fast-moving particles of galactic origin called cosmic rays.